When did bit.ly become del.icio.us?

Seriously. Props for recognizing a social media angle to what I think was just a silly side industry dominated by tiny URL until twitter got big.

Now, delicious is a personal repository and bit.ly is 2/3 tool and 1/3 social.

EDIT -- I seem to have mistaken their "history" feature for a non-existent "what's hot" feature (seemed unlikely that all that was hot was mine). Anyway, is there more value in holding their perpetual poll of websites close to their chest, or in sharing?